Plenty of home maintenance is entirely reasonable to do yourself, and there is no virtue in paying someone to change a tap washer. The question is where the line sits, and difficulty is the wrong test.
The better test: what happens if you get it slightly wrong
Painting a room badly means repainting it. Wiring a circuit badly means a connection generating heat inside a wall for years.
Both are within many homeowners’ technical capability. The consequences are not remotely comparable, and that asymmetry is what should drive the decision.
Generally fine to do yourself
Painting and decorating. Replacing tap washers, shower heads and similar fittings. Changing light fittings on existing circuits. Gutter clearing, if you are safe on a ladder. Caulking and sealing. Basic landscaping. Replacing weatherstripping. Filter changes and routine equipment maintenance.
The common thread is that the work is visible, reversible, and a mistake is inconvenient rather than dangerous.
Generally not
Electrical work beyond simple fixture swaps. Hidden, delayed and dangerous failure mode, plus permit and inspection requirements. This is the clearest case.
Garage door springs. The one job where the advice is unqualified. Torsion springs hold enormous stored energy and require specific winding bars and technique. Serious injuries from improvised replacement are well documented.
Roof work. Falls, and in Washington specifically, the temptation to pressure wash moss off — which strips the granules and takes years off the roof’s life.
Structural work. Whether a wall is load-bearing is not an on-site judgement call.
Plumbing that moves lines or opens walls. Permit territory, and hidden leaks in a marine climate become mold problems.
Gas work. Self-evidently.
The Washington-specific consideration
Our climate is unusually unforgiving of small mistakes in anything involving water management.
A flashing detail that would be marginal in a dry state fails here. A window installed without a sill pan admits water that then cannot dry, because ambient humidity is high for much of the year. A crawl space vapour barrier installed badly traps moisture rather than excluding it.
Work involving the building envelope deserves more caution here than general DIY advice written for a national audience would suggest.
Permits and insurance
Two consequences homeowners underestimate.
Permit-required work done without one surfaces at sale, and resolving it may mean opening up finished work for inspection. That cost routinely exceeds whatever was saved.
Insurance is the other. If a loss traces back to unpermitted work you performed, expect questions. This is not a reason for paranoia, but it is a reason to permit work that requires permitting even when doing it yourself.
The middle path
Often the best answer is doing part of it. Demolition, clearing a space, disposal, painting after the trades finish, and sourcing your own fixtures are all genuine savings that do not compromise the technical work.
Discuss this with your contractor rather than assuming. Many are entirely willing to price a job where the homeowner handles the unskilled portions, and some prefer it.
The honest self-assessment
Do you have the tools, the time, and a realistic plan if it goes wrong halfway through? A bathroom out of action for a weekend is fine. The same bathroom out of action for six weeks because the job got away from you is a different proposition.